A Systematic Review of Human Challenge Trials, Designs, and Safety

One of the most bizarre aspects of the COVID era was the institutional unwillingness to perform human challenge trials, which likely would have sped up vaccines and other treatments and saved lives. We let people join the military, indeed we advertise to encourage people to join the military, but for some reason running a human challenge trial is considered ethically fraught.

A new review find that HCTs are quite safe–more evidence that we have too few of these trials.

Human challenge trials (HCTs) are a clinical research method in which volunteers are exposed to a pathogen to derive scientifically useful information about the pathogen and/or an intervention [1]. Such trials have been conducted with ethical oversight since the development of the modern institutional review system of clinical trials in the 1970s. More recently, there has been renewed discussion about the ethical and practical aspects of conducting HCTs, largely fueled by interest in conducting HCTs for severe acute respiratory syndrome coronavirus 2. Past reviews of HCTs focused on reporting methods [2] and safety for single pathogens [3–6], but these did not explicitly evaluate the safety of HCTs by assessing reported adverse events (AEs) and serious adverse events (SAEs) across a range of pathogens. Furthermore, many additional HCTs have been performed since the publication of these reviews. To better inform discussions about future uses of HCTs, including during pandemic response, this article presents a systematic review of challenge trials since 1980 and reports on their clinical outcomes, with particular focus on risk of AEs and risk mitigation strategies.

Hat tip: Alec Stapp.


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